Saturn's 2-billion-year age gap problem solved

A new study has solved Saturn's two billion-year age gap problem, supporting an 80-year-old prediction. Planets tend to cool as they get older, but Saturn is hotter than astrophysicists say it should be without some additional energy source. The unexplained heat has caused a two-billion-year discrepancy for computer models estimating Saturn's age.

Models that correctly predict Jupiter to be 4.5 billion years old find Saturn to be only 2.5 billion years old, says Thomas Mattsson, manager of Sandia's high-energy-density physics theory group.

Experiments at Sandia's Z machine may help solve that problem when they verified an 80-year-old untested proposition that molecular hydrogen, normally an insulator, becomes metallic if squeezed by enough pressure.

At that point, a lattice of hydrogen molecules would break up into individual hydrogen atoms, releasing free-floating electrons that could carry a current, physicists Eugene Wigner and Hilliard Huntington predicted in 1935.

That long-ago prediction would explain Saturn's temperature because when hydrogen metallizes and mixes with helium in a dense liquid, it can release helium rain, said Sandia researcher Mike Desjarlais. Helium rain is an energy source that can alter the evolution of a planet.

"Essentially, helium rain would keep Saturn warmer than calculations of planetary age alone would predict," said Sandia researcher Marcus Knudson.